1. Field of the Invention
This invention generally relates to a network rerouting system and, more particularly, to a network rerouting system for preventing reroute overhead traffic from congesting links and overwhelming system resources.
2. Description of the Prior Art
It is well known that modern packet, frame, or cell based telecommunications reservations protocols require the reservation of bandwidth in a network for a particular connection. Generally, this bandwidth is reserved at the time the call is set up. Based on the requested bandwidth, a particular route is chosen over which the data will travel.
In certain instances, the most advantageous links may be congested at call set-up time or the requested bandwidth may not be available. This causes a reservation to be made for a connection on a route having links that are less than optimal. In other instances, the network may be in fallback mode wherein the originally reserved route for some reason, such as a link failure, becomes unavailable and the connection must be rerouted onto an alternate less optimal route. In either case, it is desirable to optimize the connection by rerouting it to a more optimal route when such a route becomes available.
Rerouting algorithms for choosing more optimal alternate data routes are known. These algorithms operate by first determining whether a more optimal route is available. If a more optimal route is available, the connection is rerouted to the new route by sending a message from a network supervisor to all the routers on both the original route and the new route.
Unfortunately, frequent rerouting can consume a significant portion of total available system resources. In particular, in a network, rerouting status and update messages are generated each time a rerouting request is made to the network. Because of the required constant monitoring of the network and the dynamic rerouting capabilities, the rerouting status and update messages in a complex network can generate significant traffic congestion on inter-router links as well as overwhelming a router's processing power. As a result, the burden of the overhead may make rerouting a less desirable option. In addition, known rerouting systems have no method of preventing reroutes based upon CPU utilization and link traffic congestion.
Therefore, there is a need for a rerouting system wherein network route optimization is allowed only when there is benefit to the connection and optimization is suspended when it is harmful to the connection.